From 0ba19c57f180c33b41c64335ea1d1c89335d34c0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Erik=20Pedersen?=
 <bjorn.erik.pedersen@gmail.com>
Date: Tue, 31 Jul 2018 11:35:38 +0200
Subject: [PATCH] tpl/partials: Add templates.Exists

Fixes #5010
---
 tpl/templates/init.go         | 44 +++++++++++++++++++++++++++++++++++
 tpl/templates/init_test.go    | 38 ++++++++++++++++++++++++++++++
 tpl/templates/templates.go    | 39 +++++++++++++++++++++++++++++++
 tpl/tplimpl/template_funcs.go |  1 +
 4 files changed, 122 insertions(+)
 create mode 100644 tpl/templates/init.go
 create mode 100644 tpl/templates/init_test.go
 create mode 100644 tpl/templates/templates.go

diff --git a/tpl/templates/init.go b/tpl/templates/init.go
new file mode 100644
index 000000000..a68809e65
--- /dev/null
+++ b/tpl/templates/init.go
@@ -0,0 +1,44 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package partials
+
+import (
+	"github.com/gohugoio/hugo/deps"
+	"github.com/gohugoio/hugo/tpl/internal"
+)
+
+const name = "templates"
+
+func init() {
+	f := func(d *deps.Deps) *internal.TemplateFuncsNamespace {
+		ctx := New(d)
+
+		ns := &internal.TemplateFuncsNamespace{
+			Name:    name,
+			Context: func(args ...interface{}) interface{} { return ctx },
+		}
+
+		ns.AddMethodMapping(ctx.Exists,
+			nil,
+			[][2]string{{`{{ if (templates.Exists "partials/header.html") }}Yes!{{ end }}`, `Yes!`},
+				{`{{ if not (templates.Exists "partials/doesnotexist.html") }}No!{{ end }}`, `No!`},
+			},
+		)
+
+		return ns
+
+	}
+
+	internal.AddTemplateFuncsNamespace(f)
+}
diff --git a/tpl/templates/init_test.go b/tpl/templates/init_test.go
new file mode 100644
index 000000000..d833cddc1
--- /dev/null
+++ b/tpl/templates/init_test.go
@@ -0,0 +1,38 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package partials
+
+import (
+	"testing"
+
+	"github.com/gohugoio/hugo/deps"
+	"github.com/gohugoio/hugo/tpl/internal"
+	"github.com/stretchr/testify/require"
+)
+
+func TestInit(t *testing.T) {
+	var found bool
+	var ns *internal.TemplateFuncsNamespace
+
+	for _, nsf := range internal.TemplateFuncsNamespaceRegistry {
+		ns = nsf(&deps.Deps{})
+		if ns.Name == name {
+			found = true
+			break
+		}
+	}
+
+	require.True(t, found)
+	require.IsType(t, &Namespace{}, ns.Context())
+}
diff --git a/tpl/templates/templates.go b/tpl/templates/templates.go
new file mode 100644
index 000000000..7a69e28a6
--- /dev/null
+++ b/tpl/templates/templates.go
@@ -0,0 +1,39 @@
+// Copyright 2018 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package partials
+
+import (
+	"github.com/gohugoio/hugo/deps"
+)
+
+// New returns a new instance of the templates-namespaced template functions.
+func New(deps *deps.Deps) *Namespace {
+	return &Namespace{
+		deps: deps,
+	}
+}
+
+// Namespace provides template functions for the "templates" namespace.
+type Namespace struct {
+	deps *deps.Deps
+}
+
+// Exists returns whether the template with the given name exists.
+// Note that this is the Unix-styled relative path including filename suffix,
+// e.g. partials/header.html
+func (ns *Namespace) Exists(name string) bool {
+	_, found := ns.deps.Tmpl.Lookup(name)
+	return found
+
+}
diff --git a/tpl/tplimpl/template_funcs.go b/tpl/tplimpl/template_funcs.go
index f1ed7f36f..27ffcd97a 100644
--- a/tpl/tplimpl/template_funcs.go
+++ b/tpl/tplimpl/template_funcs.go
@@ -40,6 +40,7 @@ import (
 	_ "github.com/gohugoio/hugo/tpl/resources"
 	_ "github.com/gohugoio/hugo/tpl/safe"
 	_ "github.com/gohugoio/hugo/tpl/strings"
+	_ "github.com/gohugoio/hugo/tpl/templates"
 	_ "github.com/gohugoio/hugo/tpl/time"
 	_ "github.com/gohugoio/hugo/tpl/transform"
 	_ "github.com/gohugoio/hugo/tpl/urls"